The present invention relates to a new and improved construction of apparatus for the irradiation of sewage waste, especially sewage sludge, with radiation having a sterilizing effect.
The sewage sludge formed during the biological treatment of sewage in a sewage treatment plant has already been pasteurized by heating the formed sewage sludge for the purpose of destroying bacteria, worms, pathogenic germs or the like. Such type treatment of the formed sewage sludge is of particular importance if the sludge is to be employed as fertilizer for agricultural purposes.
However, in order to avoid annoying odors, as such arise when thermally pasteurizing sewage sludge, it has been already proposed in the art to carry out pasteurization or sterilization of the sewage sludge with the aid of gamma radiation, following which the odorous annoyances are no longer present. Hence, there has been proposed to also effectively utilize as the radiation source, apart from e.g. cobalt 60 and cesium 137, the most powerful radiation substances of reactor wastes. In this regard reference may be made to the Swiss newspaper "Neue Zurcher Zeitung", issue published Aug. 6, 1973, No. 359, specifically the newspaper section thereof entitled "Forschung und Technik".
Furthermore, there is known in this particular field of technology a process wherein destruction of the germs or the like is effected by means of electron irradiation, the sewage sludge simultaneously being intermixed. The intermixing or agitation occurs by means of a pressurized medium, for instance compressed air, or also with the aid of pumps, there being especially utilized immersion pumps, or through the use of a stirrer or by jarring. Furthermore, for the intermixing there can be introduced into the treated material an active gas, for instance nitrogen or CO.sub.2. In this regard attention is directed to German patent publication No. 2,337,406.